RIYADH — The Interior Ministry has vowed that the masterminds behind a “cowardly” mosque attack that left 21 people dead in eastern Saudi Arabia will be arrested soon. “The terrorist attack confirms that deviant groups are seeking to create chaos (in the Kingdom),” Ministry of Interior spokesman Maj. Gen. Mansour Al-Turki told Al Arabiya News Channel, mentioning similar previous incidents including a shooting in the Eastern Province district of Al-Ahsa last year. In November, three masked gunmen attacked a group of residents in Al-Dalwah village in Al-Ahsa, killing five people and injuring nine others. “What is important now is that we find the masterminds behind this cowardly act and arrest them,” Al-Turki added. During the interview, Al-Turki also said that security forces were able to foil a terror plot after arresting a cell made up of 65 people. On Friday, a suicide bomber blew himself up during prayers at a mosque in the village of Al-Qudaih in Qatif, killing at least 21 and wounding 88 others. Injured worshippers were transferred to the Qatif Central Hospital and Aramco Hospital for treatment, according to health officials. The Ministry of Health declared a state of maximum alert for medical crews in Qatif soon after the attack. Some of the injured were treated at the scene and were provided therapeutic and ambulance services, a ministry statement said. Of the 88 injured, 58 were admitted for treatment. Thirty injured people left the hospital after receiving the necessary treatment. There are 12 critical cases, the statement said.